Anti-Roll Bar Question

  • Thread starter Litzner
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Litzner

Litzner

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United States
Traverse City, MI, USA
Priest8
Would most tuners agree that the front anti-roll bar on average needs to be a bit stronger then the rear in relationship to its corresponding springrate. I would assume this is true to better handle front weight transfer while braking, and then turning into a corner.
 
Depends on the car. Having a stronger front swaybar will create more understeer, obviously. My personal rule of thumb is that swaybar settings should be inverse of weight distribution. For example, a nose heavy car should have a soft front swaybar and strong rear, and a rear heavy car should have a strong front and soft rear. There are exceptions, of course, but in general this should help correct inherent handling balance issues.
 
oppositelock
Depends on the car. Having a stronger front swaybar will create more understeer, obviously. My personal rule of thumb is that swaybar settings should be inverse of weight distribution. For example, a nose heavy car should have a soft front swaybar and strong rear, and a rear heavy car should have a strong front and soft rear. There are exceptions, of course, but in general this should help correct inherent handling balance issues.
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I always thought the exact opposite, a front heavy car should have more swaybar to compensate for the extra weight when the front end wants to roll over.
 
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It's not about the weight of the car, it's about the drivetrain.

Usually needs:
FF cars - much softer front bar than rear.
FR - softer rear
4WD - I find that I set these even or pretty close to it.
MR - even or slightly harder rear.
 
oppositelock
Depends on the car. Having a stronger front swaybar will create more understeer, obviously. My personal rule of thumb is that swaybar settings should be inverse of weight distribution. For example, a nose heavy car should have a soft front swaybar and strong rear, and a rear heavy car should have a strong front and soft rear. There are exceptions, of course, but in general this should help correct inherent handling balance issues.
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My experience is the complete opposite. I have adjustable swaybars on my real front engine AWD car and when I set it to a stiffer setting up front and softer setting in the rear I have more oversteer. i find the same to be true in the game. i usually start with even sway bar settings on the stiffer side and will soften or stiffen the rear bar depending on how the car does on a track.
 
Sway bars are there to manage the lateral weight transfer. With cars that have an offset weight balance (61/39 for example) more weight is supported by the front, so the amount of weight supporter under lateral gs is greater. So stiffer sway bars manage that weight, while the lighter rear doesn't need as much lateral support so a less stiff sway bar can be used.

Keep in mind they need be adjusted for feel/driving style/preference.

People tune however they want, so long as the result is a better handling car to them, any way is fine.
 
GrimSinn
Sway bars are there to manage the lateral weight transfer. With cars that have an offset weight balance (61/39 for example) more weight is supported by the front, so the amount of weight supporter under lateral gs is greater. So stiffer sway bars manage that weight, while the lighter rear doesn't need as much lateral support so a less stiff sway bar can be used.

However people tune however they want, so long as the result is a better handling car to them, any way is fine.
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So you would you explain the Honda Civic race teams who run soft front sway bars 12 to 15mm and larger rear bars 19+mm? Civics carry lots of front weight.
 
Motor City Hami
So you would you explain the Honda Civic race teams who run soft front sway bars 12 to 15mm and larger rear bars 19+mm? Civics carry lots of front weight.
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They are trying to make the rear not grip so much, so it will come around. FF cars are weird lol. At least that would be my guess.
 
Another thing to keep in mind is the forward and rear rotation around the center of gravity otherwise known as "nose dive" & "rear squat" is not the "roll" but rather the "pitch" this is more managed by dampeners front to rear. The sideways lean is the "roll" that anti "roll" bars or "sway" bars deal with because the springs/dampeners at a given side of the car front/rear are the same left/right.
 
Motor City Hami
So you would you explain the Honda Civic race teams who run soft front sway bars 12 to 15mm and larger rear bars 19+mm? Civics carry lots of front weight.
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I believe I already did, reread my post to find it...

When good enough at tuning a particular vehicle for a particular class/event you become able to overcome platform shortcomings through various tuning techniques (way advanced for the average GT tuner) like getting more rotation out of a platform with the general characteristics to understeer. In this case a FF car that understeers. They use techniques to increase the rear rotation drastically like as mentioned (& correct) they reduce the rear grip to rotate it. This is all about tuning to driving feel/driving style/preference/situation/ & event and what works for you. There is nothing really set in stone. While there are many teams doing things one way there are usually other teams doing it differently.

This dawns on me to mention (should of before) but many factors come in play not just the supported weight, engine placement and drivetrain are also important to factor in. The primary factor is weight.

However using sway bars to reduce body pitch is pointless and one of the few "wrongs" as they do absolutely nothing/have absolutely no impact on the pitch (nose dive/rear squat) and literally do nothing until lateral force is applied.
 
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GrimSinn - So what are you saying, because I don't think you're being clear. Did your first post really say that if more weight is on the nose of the car, then a stiffer bar is necessary up front due to lateral loads?

And your new post now implies that for FF cars you may actually need softer bars upfront to compensate for understeer?

I'm just having a hard time following what you say. Can you simplify it a little for us non-engineers?
 
Personally with my driving style I always have my Anti-roll set to 1/1. I try to hold off and use Late braking to make up for having a slower car and when ever I set the Anti-roll to anything over 3 all I get is under-steer.
 
Motor City Hami
GrimSinn - So what are you saying, because I don't think you're being clear. Did your first post really say that if more weight is on the nose of the car, then a stiffer bar is necessary up front due to lateral loads?

And your new post now implies that for FF cars you may actually need softer bars upfront to compensate for understeer?

I'm just having a hard time following what you say. Can you simplify it a little for us non-engineers?
Click to expand...

More weight = stronger anti-roll bars.
Then adjust to driving style and track.
 
Motor City Hami
GrimSinn - So what are you saying, because I don't think you're being clear. Did your first post really say that if more weight is on the nose of the car, then a stiffer bar is necessary up front due to lateral loads?

And your new post now implies that for FF cars you may actually need softer bars upfront to compensate for understeer?

I'm just having a hard time following what you say. Can you simplify it a little for us non-engineers?
Click to expand...

It's more complex then that. The sway bars manage weight under lateral roll, nothing more.

When tuning the suspension we are manipulating the way weight is distributed under load conditions.

More lateral support is required where more weight is to balance the weight for best grip.

However (here is the kicker) once we establish the balance we can manipulate it to achieve a desired effect i.e. increase/decrease grip where we want to tune under/oversteer. That's where advanced techniques like reducing rear grip (when usually you try to increase it) to overcome a platform characteristic like FF understeer comes in.
 
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GrimSinn
It's more complex then that. The sway bars manage weight under lateral roll, nothing more.

When tuning the suspension we are manipulating the way weight is distributed under load conditions.

More lateral support is required where more weight is to balance the weight for best grip.

However (here is the kicker) once we establish the balance we can manipulate it to achieve a desired effect i.e. increase/decrease grip where we want to tune under/oversteer. That's where advanced techniques like reducing rear grip (when usually you try to increase it) to overcome a platform characteristic like FF understeer comes in.
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Right. I've raced and tuned race cars in the real world for quite some time. I understand the "facts" that you are laying out, but what is the advice that you are offering the OP to help tune better in GT5. I posted what I do to each drivetrain. I'm still trying to understand what your advice is for the OP?
 
I'm offering a better understanding of what is at play. My suggestion is always adjust for best grip based on weight, then tune for desired effect i.e. Increase/decrease under/oversteer.
 
Can I intercede here and offer my non-technical and probably what you will consider absurd take on anti-roll bars? From programming perspective though, this actually makes some sense.

Take a high powered car out on the track, tune it up. Now increase the anti-roll bars, even on the straights when there is no roll to the car, it will loose traction and spin the wheels more often. The general rule of thumb is each anti-roll bar increase needs to be offset by adding 1 or 2 dampers to the car, extension or damper or one of each.

------------------------

Spring Rates:
(FR SR + RR SR)/(Car KG/(Base RH + (RH Change/MR)))

Random Example:
(7.0 + 7.8)/(1480/(100 + (0)))
14.8/14.8 = 1.00

------------------------

Dampers:
LOG(DE) + LOG(DC)

LOG(1) = 0

LOG(3) + LOG(3)
0.477 + 0.477 = 0.954

LOG(4) + LOG(4)
0.602 + 0.602 = 1.204

LOG(5) + LOG(5)
0.699 + 0.699 = 1.398

LOG(8) + LOG(8)
0.903 + 0.903 = 1.806

LOG(10) + LOG (10)
1 + 1 = 2

LOG(5)+LOG(3)
0.699 + 0.477 = 1.176

------------------------

Anti-Roll Bars:
LN(ARB)

LN(1) = 0
LN(2) = 0.693
LN(3) = 1.099
LN(4) = 1.386
LN(5) = 1.609
LN(6) = 1.792
LN(7) = 1.946

------------------------
*BaseRH - don't ask, I'm working on it, 100 seems to work with most street cars though. (or considered (BaseRH/MR) for base = 100, mr = 1 in this example)
*MR - motion ratio

The idea being for best handling is to get all three numbers into a close range, or at minimum to have the LOGs of the combined dampers to minimally exceed either spring rate stiffness factor or the LN of the anti-roll bar in use.

You can see from a common setup of all dampers equal 8 when anti-roll bar equals 6 on many race cars, both of my comparison methods produce 1.8

Using logarithm then, each range of numbers starting with 1 is 0 or disabled or not-installed. Using the maximum range for both methods produces a maximum value near 2

I'm always tossing around theories like this, and I will continue to do so, but only under the conditions that anyone using this algorithms for a tuning application make that application not only have a free variant but also must be open source code so that other's may contribute or port to other devices or platforms. Consider it an Open Tuning Initiative.
 
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Litzner
I always thought the exact opposite, a front heavy car should have more swaybar to compensate for the extra weight when the front end wants to roll over.
Click to expand...

In my mind, that's what springs are for. Wheel rates should be more or less proportional to weight distribution, not only to ensure that both ends roll roughly the same amount but to control dive/squat and keep both front and rear suspension off the bumpstops. Swaybars should be used to alter the handling balance since they function independently and only laterally. That's my take.
 
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oppositelock
In my mind, that's what springs are for. Wheel rates should be more or less proportional to weight distribution, not only to ensure that both ends roll roughly the same amount but to keep both front and rear suspension off the bumpstops. Swaybars should be used to alter the handling balance since they function more or less independently. That's my take.
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Ok, but what about a car like my Yellowbird. I'm tuning it for the Ring'4hr right now.

Since the back is so much heavier than the front the front springs will almost double the weight put on them during heavy breaking. Do I set the front anti-roll bar for their unloaded or loaded weight? The back being so heavy barely changed its weight load compared to the front. I set he ARB for its stock weight and call it good.
 
oppositelock
Not sure I follow. Swaybars don't come into play under hard straight-line braking.
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I have noticed on cars when the stabilizers are set to a high value, particularly max (7) on the front of a car while braking hard into a corner. My theory, the stabilizer model in the physic engine (as opposed to whether it does this or not irl) is that when weight is transfered to the front, the suspension drops, and the stabilizer multiplies the drop, pulling the nose down even further, allowing greater weight transfer and burning the tires up in the process.

Edit: Also, as I pointed out in the post with my equations. The reason I went looking this relationship was a similar phenomenon occurs under straight-line acceleration with stiffer sway bars added to the rear. If you tune a car for no wheelspin, boost the rear stabilizer one setting and have wheelspin, then you generally have to add 1-2 dampers (of either type) to cancel out the additional compression under transfer, which in turn fixes the wheelspin.

Combined Damper Value makes it glorious return. Basically, everything I was ever wrong or right about in that thread cumulated into the current equation subcomponents, though I'm still far away from arranging them into a single formula.
 
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oppositelock
Not sure I follow. Swaybars don't come into play under hard straight-line braking.
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Nope, they are a bar attached from side to side one in front and one in the back. When one side is compressed more then the other (left to right) the bar twist. The thicker the bar is the more force required to twist the bar. When straight line braking the bar is not torqued at all because the left/ right sides are under the same load. It's not until lateral weight is transferred do the sway bars come into play.
 
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Im talking about trail breaking, breaking while cornering will load twice the weight on the front, doesn't that mean that there is twice the weight that the ARB must handle while cornering?

Slow in, fast out. Right?
 
I'm rather shocked that spring rate didn't even get brought up until so late in the thread.
Stiff spring, soft bar or soft spring big bar.

Regardless of what bar you use in the front, the spring rate is going to be the largest resistace to body roll. The stabalizer bar helps, but it is, quite ironicly, just to stabilize the transfer; It's not designed to be the tool that prevents the transfer.

I personally prefer softer bars up front, stiffer for the rear.
 
Adrenaline
I'm rather shocked that spring rate didn't even get brought up until so late in the thread.
Stiff spring, soft bar or soft spring big bar.

Regardless of what bar you use in the front, the spring rate is going to be the largest resistace to body roll. The stabalizer bar helps, but it is, quite ironicly, just to stabilize the transfer; It's not designed to be the tool that prevents the transfer.

I personally prefer softer bars up front, stiffer for the rear.
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As a general 'starting point' I find this is good and it works for me (highlighted above).

Since I started following this, how my cars 'feel' has definately improved, but you will still need to 'fine tune' the front and rear bars individually per car.

But generally, as Adrenaline says - soft roll bars for stiff suspension and hard roll bars for soft suspension 👍
 
This is how I've come to think about it. Why it helps or why it doesn't.
Because I find anti-roll bar settings very helpful in many cars. (Particularly FF, FR, and particularly boxy cars & antique muscle cars.) I'm not saying it's helpful for speed per se. It's helpful as to how the car feels, how stable it is.

I tend to think of it as a lurch & wallow.

Lurch I'd describe as the car seeming like it wants to roll (or slide?) off it's own wheels forward or back.

Wallow is the car seeming like it wants to roll (or slide?) off its own wheels left or right. (What someone called "lateral weight transfer"?)

Anti-roll bar tilt & level seem to be most helpful with the wallow side of things.
Ride height tilt & level seem to be most helpful with the lurch side of things.

Spring rates & dampers sort of adjust the severity of those things things happening. (I think.)

So your spring rate is going to control how much it happens. And the anti-roll bars are controlling WHERE & how, the WALLOW is going to happen or not happen.

Anti-roll bars I'm starting to think have more to do with the outcome of things rather than the cause or cure of things.
Like it's not going to govern how much something will happen. It governs how much drama is going to be the result.

And the tilt degree of the anti-roll bars - whether the stiffness is more in rear or front, determines how much unstable momentum is allowed in what direction - front or rear.

But I've yet to come to a standard for all cars or all cars of a certain type. It really seems to depend heavily on the inherent tendencies of a car, and my comfort level with some of those tendencies.
In other words, there are some tendencies that I can work with, and some I just can't. Sometimes just going faster isn't going to help me over a long run. Sometimes more stability is just favourable for the fact that at least I can be consistent & have less drama or mishaps, and that's going to make me faster in the long run than having a car that can go faster, but I'm more likely to make errors.

So I just wonder if that's why maybe whether you stiffen up or loosen up front or rear... could have less to do with what the car is doing, and more to do with how comfortable you are with the car doing what it's going to do.
?
 
ARB are great for managing over/under-steer.

Initial Tuning
Bring them up together until the car feels just right, not too tight. I usually don't go higher then 6/6 initially so I've got room to dial in the car. Stiffer spring rates can handle softer ARB settings, while soft Spring rates usually call for stiffer ARB settings.

Dialing In

Direct tuning approach
If your front is not rotating lower the front ARB, if your rear is not rotating lower the rear ARB. If your front is rotating too much increase the front ARB, if the rear is rotating too much, increase the rear ARB.

You can alternatively

Indirect tuning approach
If your front is not rotating enough, increase the rear ARB, if your rear is not rotating enough increase the front ARB. If your front is rotating too much, decrease the rear ARB. If your rear is rotating too much decrease the front ARB.

Keep in mind this is the natural rotation, neutral turns when testing initially, then progress to pushing it for dialing in.
 

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